1. Field of the Invention
The present invention relates to a recording or reading apparatus for recording or reading an image onto or from a sheet, and a sheet supply device for supplying a sheet suitable for the recording or reading apparatus.
2. Related Background Art
Conventionally, a sheet supply device has been widely used in an image recording apparatus, an image reading apparatus, and various other apparatuses, and devices with various structures and various supply methods are known. In addition, various means for realizing the function of a sheet supply device, i.e., the function of picking up one of a large number of stacked sheets, are available. In the case of devices for paper sheets, each sheet is normally picked up using a rubber roller. On the other hand, in the case of devices for films, since a sheet film has a surface roughness lower than that of a paper sheet, and tends to generate a static electricity, the attraction force between each two adjacent sheets is large when the sheets are stacked. Therefore, a method of peeling off one sheet by reducing the pressure inside a suction pad by, e.g., an electromagnetic pump is often used.
Various mechanisms for bringing the suction pad close to or away from a sheet in this case are known. For example, a suction pad moving mechanism in a sheet supply device shown in FIG. 1A is known. Referring to FIG. 1A, a sheet supply device 301 is arranged above a supply magazine 302 in which a large number of sheet films are stacked. A sheet is supplied to a pair of rollers 304 one by one while being sucked by a suction pad 303, and is then fed to an image recording/reading unit (not shown). The suction pad 303 is attached to a slide base 305, which is movable in the horizontal direction, via arms 306 and 307, and a hinge 308. The arms 306 and 307 engage with a guide groove 310 fixed to the sheet supply device via a guide pin 309. The guide groove 310 is defined by an upper guide groove 310a and a lower guide groove 310b. By switching a guide bar 311, the guide pin 309 is guided to a desired one of the guide grooves 310a and 310b. When the guide pin 309 is guided to the guide groove 310b, then the suction pad 303 moves toward the sheet film side, and when the guide pin 309 is guided to the guide groove 310a, then the suction pad 303 moves toward the pair of rollers.
FIG. 1B shows another conventional sheet supply device. A suction pad holding member 411 is supported to be vertically movable and to be pivotal about a given axis. Nipples 412 and 413 are fitted into the holding member 411, and suction pads 414 and 415 are respectively attached to the lower ends of the nipples 412 and 413. The suction pad holding member 411 is coupled, via pins 416 and 417, to the lower ends of arms 419 and 420 which are supported to cross each other and to be pivotal about a pin 418. The pin 416 is pivotally inserted in a holding hole 411a of the suction pad holding member, and the pin 417 is pivotally and slidably inserted in a guide hole 411b. The upper ends of the arms 419 and 420 are held by an arm support member 423 via pins 421 and 422, respectively. In this case as well, the pin 421 is pivotally and slidably inserted in a guide hole 423a of the member 423, and the pin 422 is pivotally inserted in a holding hole 423b. With this structure, the suction pad holding member 411 is supported to be parallel to the arm support member 423, and is movably held in a direction to approach/separate from the arm support member.
The arm support member 423 is rotatably supported by a pivot shaft 424, and the pivot shaft 424 is pivotally supported by a frame (not shown). A gear 427 is fixed to one end of the arm support member 423, and meshes with a gear 429 of a first driving source 428. On the other hand, a gear 430 is fixed to one end of the pivot shaft 424, and meshes with a gear 432 of a second driving source 431. A thread portion is formed on a portion, concealed by the arm support member 423, of the pivot shaft 424. In the arm support member 423, a slider (not shown) extends through and is supported by the pivot shaft to be slidable in the axial direction. A nut (not shown) fixed to one end of the slider is threadably engaged with the thread portion formed on the pivot shaft. The lower portion of the slider is coupled to the pin 421.
With this arrangement, when the first driving source 428 is deactivated, and the second driving source 431 is activated, the pivot shaft 424 pivots to pivot its screw portion, and the slider (not shown) moves in the axial direction. Upon movement of the slider, the pin 421 slides in the guide hole 423a, and the arms 419 and 420 pivot about the pin 418, thus vertically moving the suction pad support member 411. On the other hand, when both the first and second driving sources 428 and 431 are activated to pivot the pivot shaft 424 and the arm support member 423 at the same angular velocity, the support member 411 pivots about the pivot shaft 424 while maintaining a constant interval with the pivot shaft 424.
FIG. 2 shows an example of a sheet convey apparatus having the sheet supply device with the above arrangement.
Referring to FIG. 2, a laser optical unit 1311 deflects a laser beam 1311a, which is modulated in accordance with an image signal, using a polygonal mirror, and optically scans a film surface in the main scanning direction. A pair of sub-scanning rollers 1312 are arranged below the laser optical unit 1311, and convey a sheet clamped therebetween at a constant speed with high precision, thus attaining sub-scanning for image recording. A supply magazine 1313 for storing a stack of non-recorded sheets, and a receive magazine 1314 for storing recorded sheets are arranged below these recording means. A suction pad 1315 has a vertically movable mechanism, and picks up sheets from the supply magazine one by one. Roller pair units 1316 and 1319 are direction switching rollers which convey a sheet clamped between rollers, and controls the traveling direction of a sheet when planetary rollers 1317 and 1320 rotate around corresponding main rollers 1318 and 1321. At positions K and Q, the planetary rollers 1317 and 1320 can be separated from the corresponding main rollers 1318 and 1321, and be moved to positions L and R. A sheet registration member 1325 is used for skew registration and registration of a sheet, and its contact surface contacting the leading edge of a sheet is parallel to the main scanning line of the laser beam. Sheet guide plates 1326 and 1327 have a small frictional resistance, and guide a conveyed sheet.
The operation of an image recording apparatus with the above arrangement will be described below. When the supply magazine 1313 is loaded to a predetermined position in the apparatus main body, the suction pad 1315 is activated to pick up the uppermost sheet, and the picked-up sheet is inserted between the direction switching rollers 1316. When the planetary roller 1317 moves around the main roller 1318 at the same angular velocity from the position J to the position K simultaneously with the rotation of the main roller 1318, the traveling direction of the leading edge of the sheet is directed toward the upper second direction switching rollers 1319. When the main roller 1318 is further rotated, the sheet travels upward along the guide plate 1326, and is clamped between the second direction switching rollers 1319. The second direction switching rollers 1319 similarly convey the sheet clamped therebetween while changing the direction of the sheet by making the same motion as the above-mentioned direction switching rollers 1316. In this case, when the planetary roller 1320 moves from the position P to the position R via the position Q to be separated from the main roller 1321, the sheet travels upward while contacting the planetary roller 1320 due to its stiffness, and the leading edge portion of the sheet is directed in the direction of the registration member 1325. When the main rollers 1318 and 1321 are driven to rotate in this state, the sheet is conveyed by the first direction switching rollers 1316 while being clamped therebetween, or is moved forward by the second direction switching rollers 1319 by a frictional force generated by the stiffness and weight of the sheet itself although the planetary roller 1320 is separated therefrom. In this manner, the sheet is brought into contact with the registration member 1325. By further moving the sheet forward, the entire leading edge of the sheet contacts the registration member 1325, and as a result, the sheet is registered to be parallel to the main scanning direction of the light beam 1311a. At this time, since the sheet is moved forward while its leading edge contacts the registration member 1325, a deformation occurs on the trailing end side of the sheet, but is absorbed by a portion with a low stiffness of the sheet, as indicated by an alternate long and two short dashed line in FIG. 2.
After the registration is completed, the planetary roller 1320 is returned from the position R to the position Q, and the main roller 1321 is rotated in a direction opposite to the registration member 1325, thereby directing the sheet toward the sub-scanning rollers 1312 while maintaining a parallel state.
When the main roller 1321 is rotated in the reverse direction again, and the sheet is clamped between the sub-scanning rollers 1312, a sub-scan is immediately started, and at the same time, the light beam 1311a is irradiated from the optical unit 1311, thereby forming a predetermined image on the sheet. Upon completion of recording, the sub-scanning rollers 1312 begin to rotate in the reverse direction, and the sheet on which a latent image is recorded is conveyed in a direction opposite to the sub-scanning direction. After the sheet is clamped between the second direction switching rollers 1319 again, the planetary roller 1320 moves to the position S. With this operation, the leading edge of the sheet is directed toward the receive magazine 1314, and is fed into the magazine.
However, as a sheet supply device, a demand has arisen for a device which has a simpler structure and easier control than those of the first prior art which requires a cam switching operation, and which is suitable for vertical and horizontal movements as compared to the second prior art which is mainly vertically movable.